Re: [PATCH] crypto: loongson - Select CRYPTO_RNG

[Eric Biggers <ebiggers@kernel.org>]

On Fri, May 22, 2026 at 11:41:15AM +0800, Qunqin Zhao wrote:
> 
> 在 2026/5/22 上午10:57, Eric Biggers 写道:
> > On Fri, May 22, 2026 at 10:52:42AM +0800, Huacai Chen wrote:
> > > On Fri, May 22, 2026 at 10:26 AM Eric Biggers <ebiggers@kernel.org> wrote:
> > > > This driver registers a rng_alg, so it requires CRYPTO_RNG.
> > > > 
> > > > Fixes: 766b2d724c8d ("crypto: loongson - add Loongson RNG driver support")
> > > > Reported-by: kernel test robot <lkp@intel.com>
> > > > Closes: https://lore.kernel.org/oe-kbuild-all/202605201622.qWOiiZTV-lkp@intel.com/
> > > > Cc: stable@vger.kernel.org
> > > > Signed-off-by: Eric Biggers <ebiggers@kernel.org>
> > > Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
> > > > ---
> > > >   drivers/crypto/loongson/Kconfig | 1 +
> > > >   1 file changed, 1 insertion(+)
> > > > 
> > By the way, do any of the loongson people have any comment on what they
> > think the point of this driver is?  It's not registered with the actual
> 
> To provide an AF_ALG-based random number generation interface for other
> modules and user-space programs.
> 
> Thanks,
> 
> Qunqin

AF_ALG is a userspace interface; it's not available for in-kernel use.
If you mean using crypto_rng directly, note that no kernel code actually
uses it other than the tests, the implementation of AF_ALG, and the
FIPS-specific code which uses drbg.c specifically.

So, the first half of your justification doesn't make any sense.

As far as the second half: why would a userspace program do that instead
of just using the regular Linux RNG (/dev/urandom)?

AFAIK, the only reason to use a HW RNG directly is for certification
reasons.

However, there's also already an interface for that: /dev/hw_random.

So AF_ALG seems completely redundant for this case.

- Eric